package dk.fuddi.commons;

/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * Hex encoder and decoder.
 *
 * @author Apache Software Foundation
 * @version $Id: Hex.java,v 1.13 2004/04/18 18:22:33 ggregory Exp $
 * @since 1.1
 */
public class Hex {

	/**
	 * Used building output as Hex
	 */
	private static final char[] DIGITS = {
			'0', '1', '2', '3', '4', '5', '6', '7',
			'8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
	};

	/**
	 * Converts an array of characters representing hexidecimal values into an
	 * array of bytes of those same values. The returned array will be half the
	 * length of the passed array, as it takes two characters to represent any
	 * given byte. An exception is thrown if the passed char array has an odd
	 * number of elements.
	 *
	 * @param data An array of characters containing hexidecimal digits
	 * @return A byte array containing binary data decoded from
	 *         the supplied char array.
	 * @throws DecoderException Thrown if an odd number or illegal of characters
	 *                          is supplied
	 */
	public static byte[] decodeHex(char[] data) throws Exception {

		int len = data.length;

		if ((len & 0x01) != 0) {
			throw new Exception("Odd number of characters.");
		}

		byte[] out = new byte[len >> 1];

		// two characters form the hex value.
		for (int i = 0, j = 0; j < len; i++) {
			int f = toDigit(data[j], j) << 4;
			j++;
			f = f | toDigit(data[j], j);
			j++;
			out[i] = (byte) (f & 0xFF);
		}

		return out;
	}

	/**
	 * Converts a hexadecimal character to an integer.
	 *
	 * @param ch	A character to convert to an integer digit
	 * @param index The index of the character in the source
	 * @return An integer
	 * @throws DecoderException Thrown if ch is an illegal hex character
	 */
	protected static int toDigit(char ch, int index) throws Exception {
		int digit = Character.digit(ch, 16);
		if (digit == -1) {
			throw new Exception("Illegal hexadecimal charcter " + ch + " at index " + index);
		}
		return digit;
	}

	/**
	 * Converts an array of bytes into an array of characters representing the hexidecimal values of each byte in order.
	 * The returned array will be double the length of the passed array, as it takes two characters to represent any
	 * given byte.
	 *
	 * @param data a byte[] to convert to Hex characters
	 * @return A char[] containing hexidecimal characters
	 */
	public static char[] encodeHex(byte[] data) {

		int l = data.length;

		char[] out = new char[l << 1];

		// two characters form the hex value.
		for (int i = 0, j = 0; i < l; i++) {
			out[j++] = DIGITS[(0xF0 & data[i]) >>> 4];
			out[j++] = DIGITS[0x0F & data[i]];
		}

		return out;
	}

	/**
	 * Converts an array of character bytes representing hexidecimal values into an
	 * array of bytes of those same values. The returned array will be half the
	 * length of the passed array, as it takes two characters to represent any
	 * given byte. An exception is thrown if the passed char array has an odd
	 * number of elements.
	 *
	 * @param array An array of character bytes containing hexidecimal digits
	 * @return A byte array containing binary data decoded from
	 *         the supplied byte array (representing characters).
	 * @throws DecoderException Thrown if an odd number of characters is supplied
	 *                          to this function
	 * @see #decodeHex(char[])
	 */
	public byte[] decode(byte[] array) throws Exception {
		return decodeHex(new String(array).toCharArray());
	}

	/**
	 * Converts a String or an array of character bytes representing hexidecimal values into an
	 * array of bytes of those same values. The returned array will be half the
	 * length of the passed String or array, as it takes two characters to represent any
	 * given byte. An exception is thrown if the passed char array has an odd
	 * number of elements.
	 *
	 * @param object A String or, an array of character bytes containing hexidecimal digits
	 * @return A byte array containing binary data decoded from
	 *         the supplied byte array (representing characters).
	 * @throws DecoderException Thrown if an odd number of characters is supplied
	 *                          to this function or the object is not a String or char[]
	 * @see #decodeHex(char[])
	 */
	public Object decode(Object object) throws Exception {
		try {
			char[] charArray = object instanceof String ? ((String) object).toCharArray() : (char[]) object;
			return decodeHex(charArray);
		} catch (ClassCastException e) {
			throw new Exception(e.getMessage());
		}
	}

	/**
	 * Converts an array of bytes into an array of bytes for the characters representing the
	 * hexidecimal values of each byte in order. The returned array will be
	 * double the length of the passed array, as it takes two characters to
	 * represent any given byte.
	 *
	 * @param array a byte[] to convert to Hex characters
	 * @return A byte[] containing the bytes of the hexidecimal characters
	 * @see #encodeHex(byte[])
	 */
	public byte[] encode(byte[] array) {
		return new String(encodeHex(array)).getBytes();
	}

	/**
	 * Converts a String or an array of bytes into an array of characters representing the
	 * hexidecimal values of each byte in order. The returned array will be
	 * double the length of the passed String or array, as it takes two characters to
	 * represent any given byte.
	 *
	 * @param object a String, or byte[] to convert to Hex characters
	 * @return A char[] containing hexidecimal characters
	 * @throws EncoderException Thrown if the given object is not a String or byte[]
	 * @see #encodeHex(byte[])
	 */
	public Object encode(Object object) throws Exception {
		try {
			byte[] byteArray = object instanceof String ? ((String) object).getBytes() : (byte[]) object;
			return encodeHex(byteArray);
		} catch (ClassCastException e) {
			throw new Exception(e.getMessage());
		}
	}

}


